ZMF made its name in modification: first of the T50RP, which is one of the most commonly modified headphones in existence, they eventually made their move into wholly custom products. Although I haven't had the opportunity to hear those yet, I hope to in the future. But, I have had the time to listen, extensively I might add, to Zach Mehrbach's modification of the T50RP Mk III - the ZMF Classic. Having heard Cascadia Audio's Talos, a modification of the same headphone, this made for a great comparison point.

Talking with Zach

During the review period for these headphones, I reached out to Zach with a slew of questions, to try and get a more complete picture of the process that lead up to these headphones as his culmination of modifying the T50RP. Below, I'll collate the questions and his responses into the most legible format that I can.

Is there any information you can give as to the techniques that you employed to create the acoustic characteristics that you have in these headphones?

"Acoustically, the ZMF mod employs some driver enclosure alteration and some physical damping material. I use a couple types of foam and change the airflow of the back of the headphone and baffle. One of the biggest improvements we made was a driver enclosure mod that stabilizes the t50 driver within the enclosure. I just found that we were throwing out too many drivers, and through that frustration we developed a part to stabilize the driver which lowers the distortion and makes the headphones sound cleaner. The most noticeable thing it gets rid of is a "rattle" that is inherent to many t50's in stock form that can be heard on hard bass impacts, but it improves the sonics in many other ways including THD."

What challenges did the T50RP (or headphones to modify, in general) pose that you had to work past in designing this?

"See above. Also, the biggest challenge in modding t50's is that the headphones have great variability from the factory. So you have your target frequency response for the specific model, but then you have to do different mods to each headphone potentially to meet your target. So a good modder has to learn a plethora of techniques to make sure they are putting out a consistent product and not just a bunch of headphones with the same modification. Still there will always be variability within models, but limiting this ofcourse if the goal."

Where would you place the Classic in the rankings, sonically, of your headphones, even considering that it is the cheapest of them?

"I think the Ori and Blackwood are the best sounding depending on personal taste (some like Ori more, some like Blackwood more), but I think I took the t50 as far as I could personally go with the Classic mod. There's damping techniques and knowledge from all the other mods that went into this headphone. There's a real art to not overdamping or underdamping a headphone, and to find the "best" middleground can be very hard, and this might be the only stock t50 mod I've made that has "just" the right amount of damping. It does suffer slightly from using the original enclosure which has thin plastic walls, but the resonances are minimalized and it still keeps an amount of decay that keeps things natural. Also, when you listen to a stock t50 next to a Classic, it's pretty cool, because you can tell they are two completely different things.

Lastly, with all my other mods, I usually set out to hit a frequency response target, for the t50 mods this was the one I was able to get the closest to that target without having to sacrifice anything. That made me really proud of this work, in that I made almost exactly what I set out to do without having to compromise any area."

It's nice to see, on a more personal level, all of the work that has gone into these headphones. There is obviously a massive amount of consideration taken into account in terms of exactly what Zach is doing when he makes each headphone. Mirroring what he said at the end of that interview of sorts, I fully believe that this headphone is something to be very proud of, and I'll get to exactly why over the course of the review.

Fit and Form

I'm a big fan of the industrial look that ZMF has gone for here. Everything, from the earcups to the connectors, is heavy duty, and leaves no worry for longevity. The carbon fiber decal adds a nice little splash of texture without being overbearing.

The branding is relatively minimal, with "ZMF" stamped on the underside of the leather suspension strap, which nicely distributes the weight of the headphones across the user's head. Similarly, two stickers (one on each slider enclosure) simply say "ZMF" and either "R" or "L" to designate the right and left earcups.

I'd like to interject that the gimbal system that Fostex utilizes has been in use for a long time (since sometime around 1970), and there's a reason for that. It works incredibly well and is incredibly durable. The cable system that the T50RP uses by default, however, is not. The turning and locking mechanism of the cable can wear out the connector, causing channel imbalance, among other connectivity problems. Zach corrected this by replacing that socket with a gold-plated connector in the unbalanced version, but does something even hardier in the configuration I have. These use mini-XLR connectors with a really heavy duty balanced cable, which just adds to the industrial feel of these headphones. The cable is very well constructed, with a very heavy Y-splitter that leaves no worries of cable fray or decay over time. The connector is solid, and looks exactly like a Neutrik connector that I have on another cable, but lacks the Neutrik branding.

As an aside, the reason I requested the balanced cable with these headphones was not because I am running a balanced system. My current DAC is unbalanced, so I am not getting any of the tenuously evidenced sonic benefits from it; the benefit that I am getting is power. These are very power-hungry, and I have constantly been running them on high gain on my Neurochrome HP-1, although there is still plenty of headroom to drive these to absolutely ear-shattering volumes. They're no HE-6, but they do require some juice in order to run well.

Somehow, even with the industrial look and feel of these headphones, they remain luxurious-feeling, in use. The lambskin earpads are among the most comfortable and best-feeling that I've encountered, and make for a very pleasant experience. They are deep and wide, with plenty of room for the ear and some air in there as well. I never experienced any discomfort with long periods of use (3+ hours), The adjustment system is direct from the original headphone, and it works well, with click-less adjustment that doesn't slide around unwarranted.

Sound

Zach calls ZMF's house sound thusly, "The ZMF sound is known as a synergy between analytical and musical, with an uncanny ability to present detail without losing organic enjoyable attributes. With our headphones you'll never miss a detail, and your ears will never be fatigued." I agree, and I think that it's a good summary. Very little detail is lost in their conveyance of the music; it remains musically engaging and pleasurable while holding on to its technical competency.

The bass is slightly elevated, giving a warm tilt to the sound signature, with the mids retaining most of their forward presentation. The treble extends easily, but isn't particularly emphasized, yielding a more seemingly ensconcing sound, if that makes any sense.

Soundstage is not massive, but is very good for closed-back headphones. This makes sense, as they are only semi closed-back by nature, with venting on the backside of the earcups. Imaging and separation are good, but not exemplary, although that isn't the goal of these headphones. The music forms a very cohesive stereo image, without putting too much space between components of the track. Detail is very good, considering that I've just come off of a bunch of detail-king headphones (see my reviews of Periodic Audio's IEMs, Noble's Kaiser Encore, and King Sound's KS-H3 for reference). Not much is missed, although I will admit that they do gloss over some of the smallest micro-details of which the aforementioned headphones have made me aware.

Bass

Songs used: Lotta Years by Aesop Rock, Smoke Again by Chance the Rapper feat. Ab-Soul, and The Way It Was by Coast Modern

The best word I have to describe the bass is satisfying. It can slam hard when called upon, but also demonstrates good control in acoustic genres where it isn't necessary. Sub-bass extension is great, with a really tactile sense of rumble being present, again, when called for. The bass offers a very good supporting platform for the other frequency ranges, establishing a baseline of warmth and pleasantry that pervades the sound signature of these headphones. There's a really good sense for texture and the headphones convey a lot of the underlying complications of electronic music (beyond just low sine tones) with great fidelity.

Key descriptors: satisfying, tactile, and punchy

Mids

Songs used: Physical Education by Animals as Leaders, Scarlet Town by Chris Thile and Brad Mehldau, and Giant Steps by John Coltrane

The mids were trouble for me at first. I don't mean that they were unpleasant, but that I had a hard time putting together my thoughts. They are very natural, and can air on the side of a little bit edgy, although this was mostly when I was pushing slightly past completely safe listening levels. Once tamed, they are fairly forward, though not quite as forward as, say, the Periodic Audio Beryllium. They have a good sense for space and detail, as discussed in the "Sound" section, with each instrument finding its own place, with a good sense of connection to the whole soundstage that surrounds it. I certainly wouldn't call the mids lush, by any means, but they are not thin or anemic, either. Vocals of both genders are presented well, although the upper-mids can get the tiniest bit shouty. It wasn't always noticeable, but I did catch it enough times for me to feel that it worth mentioning.

In acoustic genres, I was particularly impressed by the realism of this frequency range. Vocals are absolutely natural, in every way, with it seeming as though the singer was right next to you. It's been a very intimate experience, in that regard. Stringed instruments are a pleasure, with every nuance of the plucking pattern being revealed by the drivers. Pianos are slightly muddier than they are when heard live, but conveying piano perfectly is something that almost every headphone I've heard struggles with, save for a very competent few.

Key descriptors: natural, realistic, and cohesive

Treble

Songs used: First by Cold War Kids, Ageispolis by Aphex Twin, and K.K.P.D. by Christian Scott

The treble is almost entirely inoffensive. Beyond that, it adds a good sense of realism to the music, with harmonic and overtones being emphasized properly. I encountered sibilance a couple times, but only in tracks that do on most headphones, and not so frequently that it became an annoyance or a problem. This range has a very good sense of poignancy and nuance, without becoming grating or unpleasant, beyond the occasional bout of sibilance that I just mentioned. Cymbals are presented with good, if even ideal, fidelity. Rides, splashes, and hi-hat barks are all extremely well-textured, especially on tracks with particularly good mixing and mastering. I oftentimes found myself caught in the drum track, as the poignancy and accuracy was very compelling once noticed.

Key descriptors: poignant, fluid, and accurate

Minutia and Miscellaneous

I don't really have much here. Zach has put together a very pleasant package, with an analytically competent sound signature while still remaining, gesturally speaking, musical. I guess my one bit of minutia is about the cable, if anything. The vast majority of non-portable headphones I've had recently come with absurdly long cables, to the point that I've just become accustomed to it. These do not, with the cable being only 1.5 or so meters long. Sure, you can't cross the room with it, but I appreciated that it stayed absolutely out of the way as a result of its length, when using it at my desk. Additionally, the way that Zach compensates for users with both single-ended and balanced amplifiers is by including the balanced cable which I discussed and, instead of a separate single-ended cable, a 4-pin XLR male to 1/4" TRS auxiliary male adapter. It struck me as smart and even innovative, as it's just a simpler and more compact way to achieve the same level of compatibility as two separate cables would provide. All of the included cables, by the way, are branded lightly with ZMF logos, which was a nice touch on their part. Purely as an aside, the cable and adapter come in separate, red and black velvet/velour bags, which was also a nice touch.

Wrap-Up

This is quite the headphone. In an industry where I feel that a lot of headphones can, in certain ways, blend together, this seems very distinct. I'll try to expand on what I mean, so as to not just make an unsubstantiated claim like that. Zach has made a headphone that blends together the analytical aspect with the musical aspect, very well. Its control of detail allows a great sense of texture and realism to the sound, while its slight bass boost and relatively forward presentation of the mids allows for a great sense of general pleasantry. It's a very appetizing listen, both when I'm looking for details, and when I'm just listening to music.

It can't compete with the likes of detail kings (like the KS-H3), but it adds a level of detail and technical competency that a lot of headphones miss, in their quest to be casually appealing. At $300, I think it's an absolutely tremendous deal as a headphone, given that you have an amplifier that can give it the power it so desperately needs. You sure wouldn't want to run these off your phone, although I'll admit that I did try, if just for kicks.

Disclaimers

These headphones were provided to me for review by ZMF Headphones. I am not being paid by anyone to write this review, to endorse the product reviewed, or for the content that I put in the review.

These headphones were powered by a Google Pixel, a Neurochrome HP-1, and an iFi Pro iCan.

I have had these headphones for about three weeks, and I have put about 20 hours of analytical listening through them during that period.